Process of treating iron-silicon alloy



UNITED STATES PATENT OFFICE.

WESLEY J'. BECK AND JAMES A. AUPPERLE, 0F MIDDLETOWN, OHIO, ASSIGNORS TO THE AMERICAN ROLLING MILL COMPANY, OF MIDDLETOWN, OHIO, A CORPORA- TION OF OHIO.

PROCESS OF TREATING IRON-SILICON ALLOY.

No Drawing.

object the forming on the surface of sheets I of such material a coating substantially im penetrable to air and moisture. The heat treatments and chemical treatments mensisting essentially of red ferric oxid (Fe,()

which ordinarily are coarse grained and loosely adherent to the metal. When silicon acts as a deoxi'dizer in the formation of oxid on the surface of the metal at atmospheric temperatures, the oXid formed is of velvety texture, black in color, and firmly adherent to the metal, the coating formed being of a cementitious nature, impenetrable to "air and moisture, and, furthermore, if this coating which consists essentially of magnetic oxid of iron (FeO,Fe,@ is broken, further action will result in replacing the coating where broken in the same manner as originally produced.

In the process of rolling such iron alloys containing silicon in substantial quantities, there is produced on the surface of the heated iron exposed to the air during rolling, a thin oxid coating. We have found that this thin coating of oxid of iron and silicon compounds is, in the usual process of Specification of Letters Patent.

' ing which with the lapse of time Patented Nov. 9, 1920.

Application filed March -19, 1919. Serial. N0. 283,579.

annealing, reduced to a loose film, consisting essentially of metallic iron, which has not been reincorporated with the body of the sheet metal, together with said silicon compounds. .Thus the finished sheet is usually covered with a thin film or skin of metal which will eventually scale off, and which is always objectionable from an appearance standpoint, but chiefly so where the sheet is to be painted soon after being placed in service. While herein referring to sheets, we merely use this term for convenience, as any shape capable of being cold-rolled is intended.

We have found that when a sheet of ironsilicon alloy containing silicon in quantities not suflicient to impair workability, preferably from five-tenths per cent. up to four and five-tenths per cent, or higher under special conditions, is first annealed, if de sired, in the usual manner and then is pickled according to the usual practice, and then given one or more passes through the cold rolls, certain chemical and physical actions result which produce a most desirable product.

Our preferred pickling bath is a solution containing approximately five percent. of sulfuric acid, the sheets being allowed to remain in the hot pickle until clean. The time and temperature of pickling are those usually employed when sheets are galvanized. W e have found that the pickling of these iron-silicon alloys dissolves the iron and leaves the silicious compounds upon the surface of the sheet which are not easily removed in the subsequent operations when the sheets are rinsed in water. lhe compounds comprise chiefly oxids of silicon together with the usual compounds resulting from pickling,-such as carbids and phosphids of iron.

We then preferably dry the sheets, although they may be left wet, and give them one or more passes through the cold rolls in the usual manner of cold-rolling, thus impregnating the surface of the sheet with the silicious material deposited thereon, forming a smooth, dense, cementitious coatfinally produces a coating impenetrable to air and moisture. This adherent film replaces the a coating stantially air and moisture-proof.

loose skin of iron above referred to and the enamel-like coating ultimately produced does not show any tendency to peel off.

Subsequent heat treatment to do away with strains should be low enough to preserve the coating.

Thus not only is the sheet provided with which with the lapse of time finally produces an air and moisture-proof enamel-like coating, but the objectionable feature of a scale on the surface of the completed sheet is done away with. For a sheet which is to be painted, the absence of this skin is very valuable. As stated in our other applications above referred to, should the coating. formed by this process and from having been exposed to atmospheric conditions, become broken, the metal beneath will provide itself with. a replacement coating of compounds of iron which are suNb- 0 technical significance is meant for thewords annealing and pickling, they being used to mean heat and acid bath treatment, and no more. The pickling solution may be hydrochloric or sulfuric acid or a mixture of the two as in ordinary practice. We have not found any reason'to exclude any known form of pickling which is useful .in our process.

The process described herein applies preferably to our iron-alloys in which substantial quantities of silicon are present,

and results in coating the metal parts which are subjectedto rolling with a firmly adherent coating, which with the lapse of time finally produces corrosion-proof skin that will not peel off. In the claims, the reference to iron alloyed with silicon is not intended to exclude the presence of other materials in the alloy.

Having thus described our invention, what we claim as new and. desire to secure by Letters Patent, is:

1. The process of treating annealed sheets of iron, alloyed with silicon which consists in pickling said sheets to leave a coating thereon'of silicious compounds, and coldrolling the sheets to impregnate the surface of said sheets with said compounds.

2. The process of treating sheets of iron alloy comprising in part silicon in such quantities as to not interfere with the workability of the product, which consists in heating the sheets, then pickling said sheets, resulting in a deposit of silicious compounds on the surface of said sheets, and finally cold-rolling the sheets so as to incorporate the silicious compounds into the surface of the metal.

3. The process of treating sheets, consisting mainly of iron alloyed with silicon, which consists of removing a dissociated film of iron and iron compounds loosely attached to the sheet, thereby leaving a coating of silicious compounds on the surface of the sheet, and cold-rolling such compounds into the body of the metal.

4. The process of treating sheets consisting mainly of iron alloyed with silicon, which consists in chemically forming a coating of silicious compounds thereon, and mechanically pressing into the surface of the sheets these silicious compounds, forming a cementitious coating with the body of the metal.

5. The ing mainly of iron and havlng a coating on the surface thereof, which consists in chemically dissolving the iron content of the surface coating, and then cold-rolling the remaining coating into the body of the sheet.

6. The process of treating sheets consisting mainly of iron which consists in chemically forming a coating on the surface thereof, and then cold-rolling said coating into the body of the sheet.

7. The process of treating sheets consisting mainly of iron and having a coating on the surface thereof which consists in chemically dissolving the iron content of the surface coating by treatment with dilute sulfuric acid, and then cold-rolling the remaining coating into the bod of the sheet.

- WESLE J. BECK.

JAMES A. AUPPERLE.

process of treating sheets consist- 

